Flowline connection means

ABSTRACT

The present invention provides a method and apparatus for connecting a flowline to a subsea structure. A riser and flowline connection tool are deployed downwardly to the subsea structure and a flowline terminal head, which is at the end of the flowline, is pulled to the flowline connection tool by means of a pullcable. Then the flowline terminal head is secured to the subsea structure and the flowline connection tool is recovered to the surface. The flowline terminal head consists of a connector hub with clamping surface to which the flowline is welded, and a flexible carrier pipe of interlocking metallic rings into which the end of the flowline is inserted. The carrier pipe limits the curvature of the flowline as the terminal head is bent into alignment with a flowline receptacle of the subsea structure. The flowline terminal head may include buoyant encircling rings which keep it free of difficult terrain in the vicinity of the subsea structure.

This is a division, of application Ser. No. 614,425, filed May 25, 1984now U.S. Pat. No. 4,620,818.

BACKGROUND OF THE INVENTION

In accordance with application Ser. No. 499,013 filed May 27, 1983, aflowline bundle is connected to a subsea production facility by using adeploy a flowline connection tool to the production facility and thenusing the flowline connection tool and a pullcable to pull the flowlinebundle to the production facility. To avoid undue stresses in theflowline bundle, due to the terrain around the subsea structures, etc.,it is necessary to prepare the terminal end of the flowline bundle sothat it may easily move over such terrain. In addition, it is desirable,once the flowline bundle reaches the subsea production facility, to havethe bundle readily securable to the facility and fluid connectionseasily made.

SUMMARY OF THE INVENTION

The primary purpose of the present invention is to provide a method andapparatus for connecting a pipeline or flowline bundle to a subseastructure, which method and apparatus are relatively simple andeconomical to use, which do no subject the pipeline or flowline bundleto dangerous stresses, which make the pipeline or flowline bundlereadily securable to the subsea structure, and which allow the fluidconnections to be easily made.

Preferably, a riser and connection tool are deployed downwardly andlanded onto the subsea structure, simultaneously as the pipeline orflowline bundle is deployed onto the seabottom a short distance away. Aterminal head at the end of the pipeline or flowline bundle is thenpulled up to the connection tool using a pullcable and a cable pullingmeans which is part of the connection tool. Next the connection tool isused to grip, orient, and bend the terminal head (through an angle up to90 degrees) as necessary to align the terminal head with a flowlinereceptacle which is part of the subsea structure. Finally, the terminalhead is secured to the flowline receptacle of the subsea structure, andthe connection tool and riser are recovered to the surface.

More preferably, after being pulled up to the connection tool, theflowline terminal head is secured to the connection tool by pulling abullnose of the terminal head into a bullnose receptacle of theconnection tool. The bullnose receptacle is then used to orient and bendthe terminal head into proper alignment with the flowline receptacle.Next, the terminal head is secured to the subsea structure by insertinga connector hub, which is integral with the terminal head, into a matingpart of the flowline receptacle. Also more preferably, the terminal headof the present invention includes a carrier pipe of interlocking ringsinto which the flowline is receivable, and this carrier pipe isencircled by buoyant rings. Most preferably, the buoyant rings aresyntactic foam of sufficient size to offset the weight of the carrierpipe, and the interlocking rings limit the bending radius of the carrierpipe, thereby protecting the pipeline or flowline bundle from buckling,etc.

Other purposes, distinctions over the art, advantages and features ofthe invention will be apparent to one skilled in the art upon review ofthe following.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows landing a connection tool onto a wellhead.

FIG. 2 discloses pulling a flowline terminal head up to the connectiontool using a pullcable and a winch which is built into the connectiontool.

FIG. 3 shows gripping and orienting the terminal head by inserting abullnose on the terminal head into a bullnose receptacle on theconnection tool.

FIG. 4 depicts rotating the bullnose receptacle downward in order tobend the flowline into alignment with the flowline receptacle on thewellhead.

FIG. 5 discloses removing the bullnose from the terminal head aftersecuring the terminal head to the flowline receptacle.

FIG. 6 discloses recovering the connection tool and riser to thesurface.

FIG. 7 provides a plan view of the wellhead, flowline, and terminal headshown in FIGS. 2-6.

FIGS. 8 and 9 show an alternative embodiment of the invention wherein alesser degree of bending is required to align the flowline with theflowline receptacle.

FIG. 10 provides a detailed view of the flowline terminal head.

FIGS. 11 and 12 disclose enlarged sectional views of FIG. 10.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is relevant to embodiments wherein an offshorepipeline or flowline bundle (both "pipeline" and "flowline bundle"hereinafter being termed "flowline") is deployed essentially verticallyto a subsea structure such as a production facility which may be anindividual subsea wellhead, a multi-well subsea template, an underwatermanifold center, a tension leg platform base structure, etc. Thisinvention pertains in particular to a method and apparatus forconnecting the flowline to the subsea production facility. During theconnection operation, the apparatus to be used with a drilling ship (asused hereinafter, "drilling ship" will include all "surface craft"suitable for deploying a "riser" or the like) will typically include ariser, a connection tool, a pullcable, a flowline, a flowline terminalhead, and receptacles for both the connection tool and the flowlineterminal head, which receptacles are part of the subsea structure. Theconnection tool is deployed at the lower end of the riser and containsremotely controlled mechanism for latching onto the subsea structure,for hauling in the pullcable and thereby pulling up the flowlineterminal head to the connection tool, for gripping and orienting theterminal head and securing it to the subsea structure, and for releasingfrom both the flowline terminal head and the subsea structure.

Applicant's co-pending applications Ser. Nos. 499,013 filed May 27,1983; now U.S. Pat. No. 4,558,971 Ser. No. 516,086 filed July 22, 1983,now U.S. Pat. No. 4,541,753 and 564,605 filed Dec. 22, 1983 now U.S.Pat. No. 4,588,326 and 614,424 filed May 25, 1984, now U.S. Pat. No.4,615,646 are incorporated herewith for more specific disclosure of theflowline connection tool and other apparatus and procedures.

The connection of the flowline to the subsea structure is accomplishedby first stationing a drilling ship over the subsea structure anddeploying a connection tool at the end of a riser down to the subseastructure, such as a wellhead. A pullcable from the connection tool isconnected to a terminal head at the end of a flowline, which terminalhead typically has flotation that permits the flowline and terminal headto be pulled across terrain surrounding the subsea structure, such asseabottom undulations, boulders, mud, etc., without damage to theflowline or terminal head. The terminal head is then pulled up to theconnection tool using the pullcable and a cable pulling means which ispart of the connection tool. Next, the connection tool is used to grip,orient, and bend the terminal head (through an angle up to 90 degrees)as necessary to align the terminal the terminal head with a flowlinereceptacle which is part of the subsea structure. Finally, the terminalhead is secured to the flowline receptacle, and the connection tool andriser are recovered to the surface.

The present invention is advantageous in comparison to the prior artinasmuch as: (1) the connection procedure is independent of the waterdepth, and therefore is especially advantageous in very deep waterswhere conventional methods are found to be difficult and tedious; (2)the flowline, flowline termination, and flowline receptacle can be madesmall and simple, since all connection operations and controls areincorporated into the connection tool and are transmitted thereto viacontrol lines in the riser; (3) field bending of the flowline intoalignment with the flowline receptacle further permits the terminal headto be small and simple, since a shop bend and stiffening means are notutilized.

Having thus generally described the apparatus and method of the presentinvention, as well as its numerous advantages over the art, thefollowing is a more detailed description thereof, given in accordancewith specific reference to the drawings.

As shown in FIG. 1, a connection tool 1, suspended from the end of ariser 2, is positioned above guide funnel 4, which is part of wellhead3. Extending outward from pull-in winch 7, which is a built-in part ofconnection tool 1, is pullcable 6. Alternatively, pullcable 6 may passdownward through riser 2 from a winch on the surface vessel, as shown bythe dashed line in FIG. 1, and then pass around pulley 7 and outwardfrom connection tool 1.

In FIG. 2, pullcable 6 is shown attached to bullnose 8 at the end offlowline terminal head 9. As shown by the direction of the arrow in FIG.2, the terminal head 9 is being pulled toward connection tool 1 bypullcable 6. The pulling only occurs after connection tool 1 is securelypositioned inside guide funnel 4 of wellhead 3 and latched onto wellheadcasing 5. Terminal head 9 has an elongated shape with a clamping surface10 between bullnose 8 and buoyancy modules 11 into which flowline 12extends. Flowline 12 is perferably welded to bulkhead 13 at the end ofthe clamping surface 10. On the opposite of clamping surface 10 frombulkhead 13 is a flowline connector hub 14 which has a built-in specialend piece to adapt to a tree connector (not shown). Hereinafterreference to the "connector hub" includes elements 10, 13, and 14.Flowline terminal head 9 is more particularly described hereinafter withreference to FIGS. 10-12.

FIG. 3 shows the procedure for gripping and orienting the terminal head9. Pullcable 6 has pulled bullnose 8 into bullnose receptacle 15 ofconnection tool 1. Now it may be necessary to rotate terminal head 9about the flowline axis until connector hub 14 is properly oriented withrespect to wellhead 3. Rotation may be necessary since there is atendency for the flowline 12 to twist as it is pulled toward connectiontool 1.

Next, the bullnose receptacle 15 is rotated downward, as indicated bythe direction of the arrow in FIG. 4, thus bending the flowline 12 andflowline terminal head 9 into alignment with the flowline clamp 17.Herinafter, reference to the "bullnose receptacle" includes both thereceptacle 15 and the mechanism 16 to which the receptacle 15 isrotatably connected, and includes the guide arm 19 of a secondembodiment of the invention. After being thus bent into position, theupper portion of terminal head 9 extends upwardly while the bottomportion extends laterally away from wellhead 3. At this time, theconnector hub 10 is gripped by flowline clamp 17. Preferably, flowlineclamps 17 are provided in two or more sites around wellhead 3, tofaciltate the laying of flowlines to the wellhead from various approachdirections.

Flowlines for subsea satellite wells and other subsea structuresnormally have sufficient wall thickness so that the pipes may befield-bent as indicated above without danger of buckling. However, foradded protection against buckling this invetion includes a carrier pipeof interlocking rings 20 which encircles the flowline, covering thelength of pipe that receives the most bending. By "locking up" at acertain predetermined curvature, the carrier pipe thereby limits thedegree of bending which that section of pipe can receive. Also, includedin this invention are a series of buoyant rings 11 which encircle thecarrier pipe. The bend-limiting carrier pipe 20 and the weight limitingbuoyant rings 11 are more particularly described hereinafter withreference to FIGS. 10-20.

The procedure for removing bullnose 8 is shown in FIG. 5. As indicatedby the direction of the arrow, the bullnose receptacle 15 is movedupwardly to remove bullnose 8 from terminal head 9, leaving terminalhead 9 suspended solely from flowline clamp 17. Bullnose 8 is leftinside bullnose receptacle 15, pending recovery of connection tool 1 tothe surface.

FIG. 6 shows recovering the flowline connection tool 1 to the surface,after having disengaged the connection tool 1 from the wellhead 3. Theflowline 12 is now properly positioned to make fluid connection with atree (not shown--to be installed later onto wellhead 3) via connectorhub 14 of flowline termial head 9.

FIGS. 8 and 9 show an alternative embodiment of the invention whereinterminal head 9 is not bent to the same degree as in the firstembodiment of the invention. Thus, an inclined flowline clamp 18 isprovided as part of wellhead 3. Bullnose 8 of flowline terminal head 9is received by bullnose receptacle 19 which is movably attached toflowline connection tool 1. Rotation of bullnose receptacle 19 downward,as indicated by the direction of the arrow in FIG. 9, bends the terminalhead 9 into alignment with flowline clamp 18.

Terminal head 9 is more particularly shown in FIGS. 10-12. Flowlinebundle 12 is welded to bulkhead 13 which is an integral part of theterminal head together with clamping surface 10 and connector hub 14.Bullnose 8 is attached to pullcable 6 and removably attached toconnector hub 14. Carrier pipe of interlocking rings 20 is attached tobulkhead 13 and encloses flowline bundle 12 over sufficient length toprotect flowlines from excessive bending. Interlocking rings 20,preferably steel, shown by the enlarged half-section view in FIG. 11,serve to limit the bend radius of terminal head 9. Buoyancy modules 11,preferably syntactic foam, fit around interlocking carcass rings 20 andare bound thereto by strap 21, preferably steel. The interlocking rings20 are preferably of an "S" shape with a space 23 being left betweentips of the S's which provides, according to the space left, limitedmovement in forming the bend radius of terminal head 9.

The foregoing description of the invention is merely intended to beexplanatory thereof, and various changes in the details of the describedmethod and apparatus may be made within the scope of the appended claimswithout departing from the spirit of the invention.

What is claimed is:
 1. A flowline terminal head comprising:a bullnoseattached at one end to a pullcable and removably attached at another endto a connector hub, the hub being functional to provide means for fluidconnection after removal of the bullnose; a clamping surface connectingthe connector hub with a bulkhead; a carrier pipe connecting with thebulkhead and enclosing a flowline bundle; interlocking rings forming thecarrier pipe and functional to limit the bend radius of the carrierpipe; and buoyant rings encircling the carrier pipe and being spacedapart at least at the outer periphery thereof to permit bending, therings being functional to prevent the flowline terminal head from deeplyplowing into the seabottom while being pulled.